Function FBmpDrawBack

xdevice.cpp:563–665

// -XI switch features.

flag FBmpDrawBack(Bitmap *bDest)
{
  Bitmap *b = &gi.bmpBack, *b2 = &gi.bmpBack2;
  int nTrans, x, y, x1, y1, x2, y2, x3, y3, x4, y4, nR, nG, nB, nRT, nGT, nBT;
  byte *pb, *pb2;
  KV kv;
  static KV kvLast = -1;
  static int nTransLast = 0, xLast = 0, yLast = 0;

  // Don't draw background if user doesn't want to.
  if (!gs.fBackDraw || !gi.fBmp)
    return fFalse;

  // Don't draw background if entire chart will be covered with world map.
  if (gi.bmpWorld.rgb != NULL &&
    (gi.nMode == gAstroGraph || (gi.nMode == gWorldMap && !gs.fMollweide)))
    return fFalse;

  // Don't do anything if bitmap empty or transparent enough to be invisible.
  nTrans = (int)(gs.rBackPct * 256.0 / 100.0);
  if (b->rgb == NULL || nTrans <= 0)
    return fFalse;

  // Cache bitmap with proper percentage blend with current background color.
  kv = KvFromKi(gi.kiOff);
  if (b2->x != b->x || b2->y != b->y || kv != kvLast || nTrans != nTransLast) {
    if (!FAllocateBmp(b2, b->x, b->y))
      return fFalse;
    kvLast = kv;
    nTransLast = nTrans;
    nR = RgbR(kv); nG = RgbG(kv); nB = RgbB(kv);
    for (y = 0; y < b->y; y++) {
      pb = _PbXY(b, 0, y);
      pb2 = _PbXY(b2, 0, y);
      for (x = 0; x < b->x; x++) {
        _GetRGB(pb, &nRT, &nGT, &nBT);
        nRT = nR + ((nRT - nR) * nTrans >> 8);
        nGT = nG + ((nGT - nG) * nTrans >> 8);
        nBT = nB + ((nBT - nB) * nTrans >> 8);
        _SetRGB(pb2, nRT, nGT, nBT);
        pb += cbPixelK; pb2 += cbPixelK;
      }
    }
    xLast = yLast = 0;
  }

  // Determine source (on bitmap) and destination (on chart) rectangles.
  x1 = y1 = x3 = y3 = 0;
  x2 = gs.xWin; y2 = gs.yWin;
  x4 = b2->x; y4 = b2->y;
  if (gs.nBackOrient < 0) {
    if ((real)x2 / (real)y2 > (real)x4 / (real)y4) {
      x2 = y2 * x4 / y4;
      x1 = (gs.xWin - x2) >> 1;
    } else {
      y2 = x2 * y4 / x4;
      y1 = (gs.yWin - y2) >> 1;
    }